Plato was the greatest student of Socrates and one of the greatest philosophers of all time. The greatest philosophers (among whom I include also Aristotle, Aquinas, Kant, and Hegel) tend to be those who bring together many ideas that at first seem disparate. As an example: Parmenides said that Being is fundamentally changeless, Heraclitus that the elements of reality are in constant change. Plato’s genius is to see truth in both of these accounts and to bring them together into a broader systematic understanding. Similarly, Plato provides distinct roles for reason and sense experience, soul and body, concepts and matter, objects and subjects, and, of course, rationalism and irrationalism.

Plato’s epistemology begins with the observation that we can learn very little from our sense organs. So far, he agrees with the Sophists. Our eyes and ears easily deceive us. But the remarkable thing is that we have the rational ability to correct these deceptions and thus to find truth. It is by our reason also that we form concepts of things. We have never, for example, seen a perfect square. But somehow we know what a perfect square would be like, for we know the mathematical formula that generates one. Since we don’t learn the concept of squareness by sense experience, we must learn it from reason. Similarly concepts of treeness, horseness, humanity, justice, virtue, goodness, and on and on. We don’t see these, but somehow we know them.

These concepts Plato calls Forms or Ideas. Since we cannot find these Forms on earth, he says, they must exist in another realm, a world of Forms, as opposed to the world of sense. But what are Forms, exactly? In reading Plato we sometimes find ourselves thinking of the Form of treeness as a perfect, gigantic tree somewhere, which serves as a model for all trees on earth. But that can’t be right. Given the many different kinds of trees, how could one tree serve as a perfect model for all of them? And even if there were a gigantic tree somewhere, how could there be a gigantic justice, or virtue, or goodness? Further, Plato says that the Forms are not objects of sensation (as a gigantic tree would be). Rather, they are known through intelligence alone, through reason. Perhaps Plato is following the Pythagoreans here, conceiving the Forms as quasi-mathematical formulae, recipes that can be used to construct trees, horses, virtue, and justice as the Pythagorean theorem can be used to construct a triangle. I say “quasi” because Plato in the Republicsaid that “mathematicals are a class of entities between the sensibles and the Forms.”[1] Nevertheless, he does believe that Forms are real things and are the models of which things on earth are copies.

The Forms, then, are perfect, immaterial, changeless, invisible, intangible objects. Though abstract, they are more real than the objects of our sense experience, for only a perfect triangle, for example, is a real triangle. And the Forms are also more knowable than things on earth. We might be uncertain whether a particular judge is just, but we cannot be uncertain as to the justice of the Form Justice. Thus, the Forms serve as models, exemplars, indeed criteria for earthly things. It is the Forms that enable us to know the earthly things that imitate them. We can know that someone is virtuous only by comparing him with the norm of Ideal Virtue.

The Forms exist in a hierarchy, the highest being the Form of the Good. For we learn what triangles, trees, human beings, and justice are when we learn what each is “good for.” Everything is good for something, so everything that exists participates in the Form of the Good to some extent. The world of Forms, therefore, contains not only formulae for making objects, but also norms defining the purposes of objects.

In Euthyphro, Socrates argues that piety cannot be defined as “what the gods desire.” For why should they desire it? They must desire it because it is good. So piety is a form of goodness, and goodness must exist independently of what gods or men may think or say about it. So it must be a Form. We should note, however, that if courage, virtue, goodness, and so forth are abstract Forms, then they have no specific content. To know what is good, for Plato, is to know the Form of the Good. But Good is what all individual examples of goodness have in common. How, then, does it help us to know specifically what is good and what is bad?

Anytime we try to define goodness in terms of specific qualities (justice, prudence, temperance, etc.), we have descended to something less than the Form of the Good. The Form of the Good serves as a norm for human goodness, because it is utterly general and abstract. Any principle that is more specific is less normative, less authoritative. Such is the consequence of trying to understand goodness as an abstract Form rather than, as in biblical theism, the will of a personal absolute.[2]

The world of sense experience is modeled on the world of Forms. Plato’s Timaeus is a sort of creation account in which the Demiurge, a godlike figure, forms matter into patterns reflecting the Forms, placing his sculpture into a receptacle (perhaps empty space, or an indeterminate “stuff” anticipating Aristotle’s matter). The Demiurge is very different from the God of the Bible, for he is subordinate to the Forms and limited by the nature of the matter. The matter resists formation, so the material objects cannot be perfect, as the Forms are. So the Demiurge must be satisfied with a defective product. It is not clear whether Plato intended this story to be taken literally. He sometimes resorted to myth when he could not come up with a properly philosophical account of something. But it is significant that he saw the need for some means to connect the Forms with the sensible world. And it is significant that he made that connection personal rather than impersonal.

But how do we know the Forms, located as we are in this defective, changing world? Here Plato reflects the subjectivism of the Sophists and Socrates: we look within. We find within ourselves recollections of the Forms. Recollections? Then at one time we must have had experience of the Forms. When? Not in this life, where our experiences are limited to imperfect and changing things, but in another life before this one. So Plato embraces the Pythagorean-Orphic doctrine of reincarnation. We lived once in a world in which the Forms were directly accessible to us. Then we “fell” from that existence into the sense-world, into bodies. Our knowledge of the Forms remains in memory, but sometimes it has to be coaxed out of us by Socratic questioning. One famous example is in Plato’s Meno, where Socrates asks questions of an uneducated slave boy, leading him to display a knowledge of geometry that nobody expected him to have.

The world of sense is not strictly knowable. Plato compares it to the shadows cast by a fire in a cave. Prisoners chained in the cave all their lives can see the shadows, but they mistake them for the truth, so in fact they know virtually nothing. Their notions are conjecture, not knowledge. We can move beyond conjecture to belief by distinguishing between images (such as shadows and pictures) and actual objects. Thus we come to know the visible world. But we do not “understand” the visible world until we see the things of the world as instances of general concepts. Thus we move from conjecture, to belief, to understanding. Pure knowledge is still a fourth stage: intuitive vision of the Forms. The first two stages Plato calls opinion, the last two knowledge. The first two come through sense experience, the last two through reason. Our sense experience is illumined by the sun; our knowledge of the intelligible world is illumined by the Form of the Good.

In Phaedrus, Plato considers knowledge from another perspective: knowledge is motivated by love. In beautiful objects,[3] we see an echo of true beauty, and we are moved by passion to seek the Form of Beauty itself. Here is another example of the Greek focus on inwardness. People have sometimes said that the search for knowledge must be disinterested, without passion. Although Plato advocated the dominance of intellect over the appetites, he saw a positive use of the passions, even in philosophy.

Since we once lived apart from the body in the world of the Forms, it must be the case that the human soul can exist separately from the body. In Phaedo, as Socrates prepares for death, he bases his hope for immortality on this epistemological argument. Plato divides the soul into three parts. The lowest is the appetitive, which seeks physical necessities and pleasures. Next higher is the spirited, which includes anger, ambition, desire for social honor, and so on. The highest is the rational, which seeks knowledge for its own sake.[4] We can see how, with a bit of emendation, these divisions correspond to the later common distinction between emotions, will, and intellect, respectively. They correspond even more closely to Freud’s distinction between id (appetitive), ego (spirited), and superego (rational). In Phaedrus, Plato sees the spirited part as a driver with two horses, white (the rational) and black (the appetitive). The spirited is swayed sometimes by the appetitive, sometimes by the rational. The more it subordinates its appetites to its intellect, the better off it will be; see fig. 2.1.

Fig. 2.1. Plato’s Analysis of the Individual Soul, with Comparisons

But Plato’s major interest, like that of Socrates, was to tell us how to live. His metaphysics and epistemology are all a prelude to his ethics and political theory. Yet it is in these areas that he is most disappointing. His Socrates discusses at length the nature of justice and courage, but comes to no firm conclusion. He does conclude that the definition of virtue is “knowledge.” One never does wrong except out of ignorance. If one knows what is right, he will necessarily do it. But most of Plato’s readers through the centuries (including his pupil Aristotle) have dismissed this statement as naive, and Christians have found it superficial in comparison with the Bible’s view of human depravity.

And if virtue is knowledge, knowledge of what? Knowledge of the Good? But good is more difficult to define than virtue is. Like all other Forms, it is abstract. So how can it settle concrete ethical disputes, such as whether abortion is right or wrong? For Plato, to live right is to know the Good. But to say that is to leave all specific ethical questions unanswered.

Plato did come to some specific recommendations in the area of politics. But these recommendations have been almost universally rejected. In the Republic, he divides the body politic into groups corresponding to the divisions of the soul. In his ideal state, the peasants are governed by the appetitive soul, the military by the spirited, and the rulers by the rational. So the rulers of the state must be philosophers, those who understand the Forms. Such a state will be totalitarian, claiming authority over all areas of life. The upper classes will share their women communally, and children will be raised by the rulers. Art will be severely restricted, because it is a kind of shadow of which one can have only conjecture, the lowest form of opinion. Images detract from knowledge of Beauty itself (the Form), and they can incite to anarchy. Donald Palmer says that Plato’s Republic “can be viewed as a plea that philosophy take over the role which art had hitherto played in Greek culture.”[5]

Most modern readers look at these ideas with distaste. Where did Plato get them? It would not be credible for him to claim that he got them by contemplating the Good. Rather, the whole business sounds like special pleading. Plato the philosopher thinks that philosophers should rule. He is rather like a Sophist here, claiming to be the expert in the means of governance. But he certainly has not shown that philosophers in general have any of the special qualities needed to govern. And the Sophists denied what Plato claims: access to absolute truth. We may applaud Plato’s rejection of relativism. But his absolutism is what makes him a totalitarian. He thinks the philosophers have Knowledge, so they must rule everything.

Plato engages in special pleading because he has no nonarbitrary way of determining what is right and wrong. But as we’ve seen, once one identifies Goodness as an abstract Form, one cannot derive from it any specific content. So Plato’s ideas about ethics and politics lack any firm basis or credibility.

The best thing that can be said of Plato is that he knew and considered seriously the criticisms that could be made against his system. He treats a number of these in the Parmenides, without actually answering them. In this dialogue, Parmenides asks the young Socrates whether there are Ideas (Forms) of such things as mud, hair, and filth. He might also have asked whether there are Ideas of evil, of imperfection, of negation. But how can there be a Form of imperfection, if the Forms by definition are of perfection? But if there is no Form of imperfection, then the Forms fail to account for all the qualities of the material world.

Another objection (called the third man): if the similarity between men requires us to invoke the Form Man to account for it, then what of the similarity between men and the Form Man? Does that require another Form (a Third Man)? And does the similarity between the second Form and the third Form require a fourth, ad infinitum?

The first objection shows that the Forms are inadequate to account for experience. The second objection shows that on Plato’s basis the Forms themselves require explanation, and that they are inadequate to provide that explanation themselves.

Plato also explores other objections to his theory that I can’t take the time to describe here. The main problem is that the Forms cannot do their job. The Forms are supposed to be models for everything in the sensible world. In fact they are not, for perfect Forms cannot model imperfection; changeless Forms cannot model change. So the imperfection and change of the experienced world have no rational explanation. Plato tries to explain them by the story of the Demiurge in Timaeus. But that, after all, is myth. Plato gives us no reason to believe in a Demiurge, and in any case the Demiurge does not account for the existence of matter or the receptacle. So the changing world of matter and space is for Plato, as for Parmenides, ultimately irrational. Parmenides had the courage to say that the changing world is therefore unreal. Plato does not go quite this far; rather, he ascribed a greater degree of reality to the Forms than to the sense-world. But we must question Plato’s assumption that there are degrees of reality. What does it mean to say that one thing is “more real” than another?

The picture should be clear by now. Though Plato is far more sophisticated than the pre-Socratics, his position, like theirs, incorporates rationalism and irrationalism. He is rationalistic about the Forms, irrationalistic about the sense-world. For him, reason is totally competent to understand the Forms, incompetent to make sense of the changing world of experience. Yet he tries to analyze the changing world by means of changeless Forms, an irrational world by a rationalistic principle. Eventually, in the Parmenides, he has the integrity to admit that his fundamental questions remain unanswered; see fig. 2.2.

Fig. 2.2. Plato’s Rationalism and Irrationalism

With Plato as with the pre-Socratics, the tension between rationalism and irrationalism has a religious root. If Plato had known the God of Scripture, he would have known in what fundamental ways our reason is competent, yet limited. And he would have understood that the world of change is knowable, but not exhaustively, because God made it that way. He would also have been able to consult God’s revelation for ethical guidance, rather than teaching his students to rely on the abstract Form of the Good, which has nothing specific to say to them.

John Frame is the author of many books, including the four-volume Theology of Lordship series, and previously taught theology and apologetics at Westminster Theological Seminary (Philadelphia) and at Westminster Seminary California.

John M. Frame (BD, Westminster Theological Seminary; AM, MPhil, Yale University; DD, Belhaven College) is J. D. Trimble Professor of Systematic Theology and Philosophy, Emeritus, Reformed Theological Seminary, Orlando.

[1] Diogenes Allen, Philosophy for Understanding Theology (Atlanta: John Knox Press, 1985), 20. Allen’s further comments on this issue are helpful.

[2] And if anyone asks the relation of goodness to the God of the Bible, the answer is as follows: (1) Goodness is not something above him, that he must submit to; (2) nor is it something below him, that he could alter at will, but (3) it is his own nature: his actions and attributes, given to human beings for imitation. “You therefore must be perfect, as your heavenly Father is perfect” (Matt. 5:48).

[3] His example is the beauty of a boy, as a pederastic love interest. As did many other Greek thinkers, Plato favored homosexual relationships between men and boys, another indication of how far the Greeks were from the biblical revelation. Paul’s argument in Romans 1 presents homosexuality as a particularly vivid example of the depths to which people fall when they reject God’s revelation.

[4] In Phaedo, the soul is only the higher part, but in Phaedrus, the soul includes all three parts, even prior to its bodily existence.

[5] Donald Palmer, Looking at Philosophy: The Unbearable Heaviness of Philosophy Made Lighter (Mountain View, CA: Mayfield Publishing, 1994), 73.